In the area of water treatment, such as ground water or industrial waste water treatment, there is an ever-increasing need to remove undesirable and even toxic contaminants, particularly heavy metal contaminants, from water. Many industrial processes utilize aqueous solutions of heavy metals, such as lead in the manufacture of batteries, and chromium or copper in electroplating solutions.
Unfortunately, the removal of such heavy metals from the aqueous solutions used in these processes has proven to be not only difficult but expensive. Prior art processes have utilized different types of adsorbents, such as activated carbon, activated sludge, various types of natural clays, carbon aerogels, coirpith carbon, natural zeolites and even date pits. Likewise, heavy metal removal can be accomplished through expensive ion exchange resins.
Tarao et al. (U.S. Pat. No. 4,133,755) discloses agents for removing heavy metals comprising a composition consisting mainly of a dithiocarbamate bond-containing low molecular weight compound, amorphous silica and activated carbon powder, granulated with a vinyl acetate polymer binder and clay as a thixotropic excipient. Tarao et al. disclose packing the granulated materials into columns for treating mercury-contaminated waste water.
Cody et al. (U.S. Pat. No. 5,667,694) discloses a process for removing dissolved heavy metals including lead and radioactive contaminants from contaminated aqueous systems including aqueous soil systems. An organically modified smectite clay, or organoclay, is used to treat these systems. Organoclays are the reaction product of smectite clays and quaternary ammonium compounds. The organoclay is brought in contact with system to be treated where it absorbs the heavy metal in the aqueous system onto the organoclay which absorbed complex is then removed by a variety of methods including flotation and air sparging.
Oomura et al. (U.S. Pat. No. 5,256,615), discloses a granular inorganic ion exchanger which is obtained by firing at 400° C. or higher a granular molded product of a mixture of a metal alkoxide such as Si(OMe)4 or hydrolyzate thereof, a clay mineral such as sepiolite and an inorganic ion exchanger such as antimony pentoxide and which has mechanical strength and heat resistance without losing its inherent ion exchangeability.
Payzant et al. (WO0072958) discloses a networked polymer/clay alloy produced from a monomer/clay mixture comprising a monomer, a cross-linking agent and clay particles. The clay is chemically integrated with the polymer such that, on exposure to water, the networked polymer/clay alloy swells with substantially no clay separating from the alloy.
However, none of the above-discussed references discloses or suggests a relatively inexpensive but highly effective adsorbent composition for removal of heavy metal contaminants from contaminated water streams. Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.